Welding structure and welding method

Abstract

A welding structure ( 30 A) includes a welding layer ( 60 A) which is configured of a first built-up layer ( 33 ) which is formed of low-alloy steel or carbon steel having a carbon content of less than low-alloy steel and which is formed on a base metal ( 31 ), a second built-up layer ( 34 ) which is formed of a 600-type nickel-based alloy and which is formed on the first built-up layer ( 33 ) and a third built-up layer ( 35 ) which is formed of a 690-type nickel-based alloy and which is formed on the second built-up layer ( 34 ).

1 . A welding structure comprising:
 a first base member formed of low alloy steel; and   a welding layer formed on the first base member,   wherein the welding layer includes:   a first built-up layer which is formed of low-alloy steel or carbon steel with a low carbon content of less than the low-alloy steel and which is formed on the first base member; and   a second built-up layer which is formed of one of a nickel-based alloy and stainless steel and which is formed on the first built-up layer.   
     
     
         2 . The welding structure according to  claim 1 ,
 wherein the welding layer further includes a third built-up layer which is formed of a nickel-based alloy having a nickel content of less than the second built-up layer and a chromium content of larger than the second built-up layer, and which is formed on the second built-up layer.   
     
     
         3 . The welding structure according to  claim 2 ,
 wherein the welding layer further includes a joint welding layer which is formed of the nickel-based alloy similar to the third built-up layer or stainless steel, and which joint welds the third built-up layer and a second base member formed of the stainless steel or the nickel-based alloy.   
     
     
         4 . The welding structure according to  claim 1 ,
 wherein carbon content of the low-alloy steel or the carbon steel with a low carbon content is 0.1% or less.   
     
     
         5 . The welding structure according to  claim 1 ,
 wherein the nickel-based alloy configuring the second built-up layer is a 600-type nickel-based alloy, and   wherein the nickel-based alloy configuring the third built-up layer is a 690-type nickel-based alloy.   
     
     
         6 . The welding structure according to  claim 1 ,
 wherein the nickel-based alloy configuring the second built-up layer is a 600-type nickel-based alloy, and   wherein the stainless steel configuring the third built-up layer is 308-type or 308L-type stainless steel.   
     
     
         7 . The welding structure according to  claim 1 ,
 wherein vanadium or niobium is added to the low-alloy steel or the carbon steel with a low carbon content configuring the first built-up layer.   
     
     
         8 . A welding method for forming a welding layer on a first base member formed of low-alloy steel, the method comprising:
 a first welding process of forming a first-built up layer by performing built-up welding to the first base member by using low-alloy steel or carbon steel having a carbon content of less than the low-alloy steel;   a second welding process of forming a second built-up layer by performing built-up welding to the first built-up layer by using a nickel-based alloy or austenitic stainless steel; and   a heat treatment process of performing heat treatment after welding to a heat-affected zone of the first base member which is generated by the first welding process.   
     
     
         9 . The welding method according to  claim 8 , further comprising:
 a third welding process of performing built-up welding to the second built-up layer by using a nickel-based alloy or stainless steel, which has a nickel content of less than the second built-up layer and a chromium content of larger than the second built-up layer, as a third built-up layer,   wherein the third welding process is performed after the second welding process and before the heat treatment process.   
     
     
         10 . The welding method according to  claim 8 , further comprising:
 a fourth welding process of forming joint welding layer by performing joint welding to the third built-up layer and a second base member formed of the stainless steel or the nickel-based alloy through the nickel-based alloy or stainless steel,   wherein the fourth welding process is performed after the heat treatment process.   
     
     
         11 . The welding method according to  claim 9 , further comprising:
 a fourth welding process of forming joint welding layer by performing joint welding to the third built-up layer and a second base member formed of the stainless steel or the nickel-based alloy through the nickel-based alloy or stainless steel,   wherein the fourth welding process is performed after the heat treatment process.